The invention relates generally to a method and device for the performance of a supporting function in a passage. Although a particular aspect of the invention is directed to a method and device for forming a passage in an element made of a flowable and hardenable material, e.g., concrete or the like, the invention also encompasses the performance of other supporting functions in a passage.
It is frequently necessary to provide a passage in an element cast from concrete. In particular, an element cast from concrete often requires a passage for anchoring a lifting member to transport and/or mount the element.
A known lifting member has a shaft which extends into the interior of the concrete element in a direction generally perpendicular to a surface of the element. The end of the shaft inside the element is provided with an anchor which releasably engages the concrete element. The passage for the lifting member is lined with a hollow member which conforms to the contour of the lifting member and extends into the interior of the concrete element in a direction perpendicular to the above-mentioned surface of the element.
In order to define the passage for the lifting member and to prevent the hollow member from being filled during pouring of the concrete, it has become known to insert a resilient, one-piece plug in the hollow member prior to pouring. A screw extends through the plug and is operative to compress the plug axially so that the plug is pressed against the walls of the hollow member and thereby seals the same (see, for example, DE-OS No. 1961 879). The plug is intended to be removable after the concrete has set.
It has been found that considerable difficulties are encountered during removal of the resilient plug. Thus, once the concrete has been poured, the plug becomes fixed in the hollow member in such a manner that the screw which extends through the plug and is to be used in removing the plug further compresses the same. This causes the plug to be pressed against the walls of the hollow member more forcefully. Accordingly, the removal of such a resilient, one-piece plug cannot always be performed in a satisfactory manner, e.g. it may be necessary to destroy the plug in order to expose the anchoring passage.
It is further known to seal the hollow member with a three-piece shaft or the like. One of the sections of a plug of this type is in the form of a wedge which is removed during disassembly. Plugs of this type are not only expensive and difficult to handle but require substantial forces to separate the individual sections from one another. Moreover, such plugs are not effective for sealing the hollow member against the fine particles which accumulate in the region of the hollow member during setting of the concrete. Other difficulties also arise on occasion when using plugs having multiple sections.